Did you expect San Diego State to put away Boise State in the quarterfinals of the Mountain West tournament Wednesday night when it led by 11 points in the first half or 13 midway through the second, or when star Broncos star guard Derrick Marks missed his first 12 shots and didn’t score for the first 27-plus minutes?

Did you expect a game between these teams to be anything but a down-to-the-wire, peek-through-your-hands thriller?

But give the Aztecs this much: They teetered on the edge of the precipice, lost their balance a few times, wavered and wobbled, looked into the abyss below ... and never fell off. Their 73-67 win against Boise State at the Thomas & Mack Center puts them Friday’s 6 p.m. semifinals against top-seeded New Mexico and almost certainly into the NCAA Tournament the following week.

You can exhale now.

The team that couldn’t win the close ones all season won the close one when it mattered most.

“Just like football,” SDSU students who made the trip chanted from the Thomas & Mack rafters as the final seconds ticked away, referring to the Aztecs’ upset in Boise last fall to claim a share of the Mountain West title.

And not like Saturday. The Aztecs lost 69-65 at Boise, the fourth time in the last five meetings between the teams that it has been a one-possession game in the final minute.

This was more of the same. “A little bit of a carbon copy,” SDSU coach Steve Fisher said.

The Aztecs blew a 13-point lead in a mere 3:20 thanks to a flurry of turnovers (they finished with 19) and suddenly found themselves needing to, as Fisher has said over and over this season, “make a play” in crunch time.

It came, of all people, from freshman Winston Shepard.

He had been having a nightmarish game, with five turnovers and four missed free throws and that glazed look regularly seen across the face of freshmen in big games. A less patient, less seasoned, less savvy coach would have unceremoniously yanked him long ago.

But Fisher didn’t, partly because four decades of experience told him not to and partly because Shepard also had seven rebound and three blocks. And partly because he didn’t have much choice, with his bigs in foul trouble and Boise State making the radical decision to play five guards.

So there was Shepard in the left corner, with the Aztecs up 61-57 inside a minute to go and the shot clock running down and Jamaal Franklin trying to create something out of nothing. Franklin (19 points, eight rebounds, four assists) drove, was stopped, rose up and found Shepard cutting behind his defender along the baseline.

The freshman muscled up a shot, scored was fouled and made the free throw for a 64-57 lead with 58 seconds left.

The Aztecs (22-9) are now 11-2 at the Mountain West tournament over the past five years, and if they beat New Mexico it will be their fifth straight trip to the championship game. Senior Chase Tapley won at Thomas & Mack for the 10th time in his career, counting the conference tournament and regular-season games against UNLV.

“We knew we were playing a team that’s really, really good,” Boise State coach Leon Rice said. “They were dialed in. They played terrific defense. Got us a little flustered.”

Especially Marks, who had 27 points Saturday and made one did-he-just-do-that shot after another down the stretch.

The Aztecs tweaked their defense from Saturday’s game and switched all the perimeter screens and dribble hand-offs. They pressured the ball on the perimeter more. They helped less off the shooters.

They also installed a package to double-team Marks. Didn’t need it. Instead they were content to let him keep shooting, and he was 0 of 12 with no points until he made a pair of free throws with 12:09 to go.

The Aztecs went to the other end and Tapley (17 points, six rebounds, four steals) made his third 3-pointer in 4½ minutes to give them their largest lead at 49-36. All was well, right?

Wrong. Marks was just getting heated up, it turned out. A 14-0 run later, including two deep 3s by Marks, and the Broncos had their first lead at 50-49 with 8:28 remaining.

“I knew eventually I would just make one,” said Marks, who finished with 14 points on 4-of-22 shooting.

The Broncos regularly play one post and four guards. Rice took to another level, replacing a big with 6-foot-4 Thomas Bropleh midway through the second half and rolling the dice with five guards.

“It’s funny to say we went small ball because we started small ball,” Rice said. “We just went smaller ball.”

The Aztecs countered with 6-7 JJ O’Brien and four guards. When O’Brien fouled out with 2:52 left and a two-point lead, they shrugged and went with five perimeter players as well.

“It was five guards against five guards – it was like rec ball out there,” Dutcher said. “You spend all year playing with at least one big in there, and now you have to figure it out with five guards, figure out who knows what positions and what plays we can run.”

In the end, the Aztecs figured it out better. They took 18 fewer shots than Boise State and surrendered 12 offensive rebounds and coughed up those 19 turnovers. But they got to the line 31 times and made 25 (80.6 percent), and Xavier Thames had another big game with 18 points, six rebounds and five assists.

Instead, it’s Boise State that will spend the rest of the week sweating out their NCAA Tournament fate as the 10-person selection committee assembles in Indianapolis, wondering if a 9-7 record in the nation’s top-rated conference and a RPI hovering around 40 is enough for an at-large berth.

Fisher thinks it is.

“This league is so good, if Boise doesn’t get in the tournament I’m going to demand a revote,” he said. “They’re that good … I’ll repeat myself. Boise better be in the NCAA Tournament or it’s disgraceful, in my opinion.”

Notes

The streak of victories while leading with five minutes to go lives on. The Aztecs led 55-50 Wednesday and extended the streak to 91 straight … This is SDSU’s sixth straight year in the semifinals, the longest active streak in the conference. New Mexico and UNLV have each reached four straight semis … Franklin went 2 of 3 behind the arc, making him 12 of 21 on 3s over his career in the Mountain West tournament … Only SDSU’s PR staff could dig this one up: The Aztecs are 21-6 in their last 27 games played on a Wednesday.